In a vehicle, for example, source power is required to be appropriately supplied to a large number of various electric components from an alternator (generator) or a battery which is a main power source. A system used to supply such source power is also required to have a function of switching between ON and OFF of the supply of power as necessary, or a function of cutting off a current for each system in a case where an excessive current flows through an electric component.
In a general vehicle, a wire harness which is an aggregate of a plurality of electric wires is routed on the vehicle, and a main power source is connected to electric components at each location via the wire harness so that power is supplied thereto. Generally, a junction block is used to distribute source power to a plurality of systems, a relay box is used to control ON and OFF of the supply of power for each system, or a fuse box is used to protect each electric wire or a load of the wire harness.
The vehicle is provided with a plurality of control units for controlling the electric components, and the control units and the electric components are communicably connected to each other via the wire harness.
For example, a wire harness disclosed in Patent Document 1 includes a network transmission path and a circuit for providing power, GND and other signals. The wire harness includes a wire harness trunk line, a sub-wire harness, an optional sub-wire harness, and a network hub device.    Patent Document 1: JP-A-2005-78962